Designing FlexLED 2.0

Designing FlexLED 2.0


so one of the projects that I think has the most potential is FlexLED so I want to design a second version of it if you have absolutely no idea of what I’m talking about FlexLED is my attempt in trying to create a simple POV display it just have a neodymium magnet and an LED soldered on a flexible PCB which creates this flapping motion I’ve already made a video about this but now I want to create a larger version with more LEDs okay so here’s what I was thinking I made the row of 8 LEDs which for the next prototype I think is enough and I decided to make two coils the reason why I made two coils and not one large coil is because I don’t think one coil can be able to withstand the load of the 8 LEDs so I decided to share it to check how it affects its behavior I have glued some LEDs on the coils so this one has 8 LEDs and this one has 4 and this way we should compare them so this is the four LED version and this is the eight there’s not much of a difference but I think for the second prototype it’s safer to go with four LEDs per coil the disadvantage of having eight LEDs is that we have to pass all their traces from the two ends now we could also add an LED driver very close to the LEDs but we would also be increasing the weight at the very end which would probably make the coils flap less and therefore decreasing the resolution of our POV display okay so I have opened this new PCB project on Altium we need to start by knowing which area
we have available so the best thing to do is start with the coils for this project I’m going to use the same PCB coils that I’m using for the Flexbot so this coil has around 70 turns with a width and clearance of around 0.1mm so from this shape it’s pretty clear that the LEDs needs to come
somewhere over here I did alot of research trying to find the best right-angle LED possible for this project and this is the best one that I could find It is an RGB LED that has this very thin and sort of long profile what’s very good
about it is that it takes the least amount of space possible which is going
to allow us to reduce this region over here and also place the LEDs closer
together so this is where we are I have passed all the LED traces in the top and bottom layer the only track that I forgot to
pass is the anode of the LEDs but thankfully we can eliminate
two wires from one of the coils because it can be connected in parallel
to the other one we just need to make sure that both
coils obey the right-hand grip rule okay so now we need to start think about
the electronics we have a total of 8 LEDs and each LED has 3 LEDs
so total of 24 LEDs so we clearly cannot drive these LEDs
individually so we need an LED driver a 24-channel a LED driver we also need an h-bridge to drive the coil a microcontroller that handles the LED driver and drives the coil and we also need some form of external
communication to tell the microcontroller what LEDs it should be driving so I think that should be UART the next step is finding our components let’s start with the LED driver this is what I’m going with this LED driver has 24 constant current output channels that can go up to 50 milliamps and then this current can be controlled individually
on each channel with a 7 bit resolution and on top of that we have an extra 12
10 or 8-bit PWM adjustment it can also detect if an LED
is open or short circuit all this is being done by a serial data interface which basically
means that works like a shift register so now that we have a general idea of
how the LEDs are going to be driven let’s start building the schematics so I think we’re finished we have the LED driver a cheap little 8-bit PIC the h-bridge which is driving the coil an lc filter to make sure that our microcontroller is safe the programming connector and the UART and power connector so I think we can just go
ahead and import the components these connectors are huge so let’s make the board a little larger okay so I’m not very happy with having these connectors
mounted on a flexible PCB the PCB would be too thin
to hold them firmly in place so I think I have to turn this
into a flexi rigid PCB I have to be honest with you I have
never designed a flexirigid PCB so bear with me because there’s
going to be a little learning curve the first thing that we have to do
is add two extra layers to our PCB we also have to define the
layer stack for the flexible region which is going to be made from
the top layer and the one just underneath it here’s where I got a little stuck because Altium 19 had added some new
features that I was not aware of the first thing was that I had the stack
symmetry box ticked which was not allowing me to select the layers that I
wanted but then I got it sorted and shifted all the tracks from the
bottom layer to layer 1 after defining the split lines and dividing
the board into two different regions the bend line I made was not working and this was because I
missed this other tick box here all this hassle to make a bend line
was not actually required to design a flexi rigid PCB but Altium has this
cool little feature that I had to try what is really required is this little
note on this mechanical layer here which basically lets the PCB manufacturer know
which area is flexible and which area is fr4 now on the bottom side I was
thinking of mounting the magnet I have drawn the magnet in fusion 360 now we just need to import it in Altium our magnet is almost taking all of our PCB area except for this region over here so most of the electronics have to be
mounted to the other side what do you think it’s pretty much completed there only these errors left
which are related to the fact that our coil has no net other than that I’m pretty happy with how it turned out okay so now that we have the PCB finished I want to make a little 3d printed case for the bottom base I know it’s bulky but for now remember that this is just a proof of concept so we can always try to make it slimmer later what’s really interesting about
this is that I tried to make it from just one whole part and to do that I had
to make this little slot for the flexible part to just slide in here I made a little pocket for the magnet so that then all I have to do is fasten
four screws to keep both the PCB
and the magnet in place the last thing I want to
show you is how easy it is to order a flexi rigid PCB it may look something
complicated for beginners but PCBway makes it super easy their ordering page for flexi rigid PCBs is basically divided into three the first part is where you
specified the mechanical specifications of your whole board then there are another two sections where you define the thickness
and solder mask colors for both the Flex
and the rigid parts it’s just simple as that PCBWay has been very loyal to my
channel and again they’re going to help me bring this project to life by
sponsoring these PCBs I highly recommend you check them out and they also gave me this coupon
code that you guys can use to get 10$ off your orders so I think that’s about it these PCBs will arrive here in a couple of days but than I will have to solder them test them and write software for them but that will be a whole other video so please make sure you subscribe so you don’t miss it thank you for watching


25 thoughts on “Designing FlexLED 2.0

  1. When soldering the LEDs you add more weight with more solder, therefore reducing the leg count and also the pad size will be helpful. It was a good choice to pick RGB LEDs, since they have common Anode or Cathode, which saved 2 legs and 2 pads for every 3 diodes. I have used similar LEDs in the past and was not happy with them at all. They were very sensitive to high temperature and were bending in the soldering process. Another downfall on them was the way you see the 3 individual diodes when lit. But mine were by Everlight and yours are by Citizen, presumably better. I'm looking forward to seeing how do you like those.

  2. have you thought about using LEDs with built-in driver, such as WS2812 etc.? they require only 3 wires (Vcc, GND, D) and shouldn't weight much more than RGB 4pin LEDs I think.

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